The invention relates to an expansible fixing plug.
Such an expansible fixing plug is known from DE 43 17 039 A1. The known expansible fixing plug has disc-shaped expansion elements in an expansion region extending over part of the length of the expansible fixing plug, the disc-shaped expansion elements being arranged perpendicularly to the lengthwise direction of the expansible fixing plug. The expansion elements are provided with an expansion hole passing through them in the lengthwise direction of the expansible fixing plug, the expansion hole being arranged eccentrically in the disc-shaped expansion elements. In this connection, the expansion holes of adjacent expansion elements are arranged offset in opposing directions in the expansion elements. The expansion holes in the expansion elements form in the expansion region of the expansible fixing plug an expansion channel, which is constricted by the expansion holes arranged eccentrically alternately in opposite directions. To expand the known expansible fixing plug, a pin-shaped expansion element, for example, an expansion nail or an expansion screw, is inserted in the expansion channel of the expansible fixing plug. The pin-shaped expansion element aligns the expansion holes in the expansion elements so that they lie on the same axis as one another, the disc-shaped expansion elements being displaced in the radial direction of the expansible fixing plug. In the process, adjacent expansion elements are displaced in opposite directions. The expansible fixing plug is consequently expanded and anchored in a drilled hole.
For fixing the expansion elements, in its expansion region the known expansible fixing plug has two longitudinally extending fixing webs, which are arranged opposite one another at the circumference of the expansible fixing plug. The disc-shaped expansion elements are each connected to a fixing web, from which they project at right angles towards the other fixing web. In this connection, every other expansion element is connected to one fixing web and the expansion element in between is connected to the other fixing web, so that the disc-shaped expansion elements are interleaved. The fixing webs are arranged at right angles to the direction in which the expansion holes are arranged eccentrically in the expansion elements. As the expansible fixing plug is expanded, the fixing webs are displaced parallel to one another in opposite directions and are not expanded radially apart. As the expansible fixing plug is expanded, the expansion elements, not the fixing webs, are therefore pressed directly with their circumferential edge against the wall of a drilled hole.
The invention is based on the problem of proposing an expansible fixing plug of the kind mentioned in the introduction having increased anchoring force (withdrawal force) in a hole drilled in masonry.
That problem is solved in accordance with the present invention. The expansible fixing plug according to the invention has expansion ribs as expansion elements, which are arranged approximately in radial planes of the expansible fixing plug and which enclose the expansion channel for part of the circumference of the expansible fixing plug. In this connection, expansion ribs adjacent to one another in the lengthwise direction of the expansible fixing plug are arranged at different points on the circumference, for example, opposite one another. Inner edges of the expansible ribs define the expansion channel at the circumference thereof and constrict the expansion channel. By inserting a pin-shaped expansion element, the expansion ribs are pressed radially apart in different directions and hence the expansible fixing plug is expanded. Constriction within the meaning of the invention shall be understood to mean that the expansion channel defined by the inner edges of the expansion ribs has a smaller inside width than a transverse dimension or diameter of the pin-shaped expansion element that is used to expand the expansible fixing plug.
The expansion ribs are fixed to circumferential wall portions, each of which extends only for part of the circumference of the expansible fixing plug and which together at least approximately completely close the expansible fixing plug circumferentially in the unexpanded state of the expansible fixing plug. The expansion ribs project inwards from the inner sides of the circumferential wall portions, adjacent expansion ribs being disposed on different circumferential wall portions. The expansion ribs are interleaved, to the extent that they overlap one another viewed in the lengthwise direction of the expansible fixing plug.
To expand the expansible fixing plug according to the invention, a pin-shaped expansion element is introduced into the expansion channel of the expansible fixing plug. This expansion element presses the expansion elements radially apart in different directions, with the result that the circumferential wall portions, from which the expansion ribs project inwards, are likewise pressed apart, that is, are expanded. By inserting the expansion element into the expansion channel, the circumferential wall portions are pressed radially apart. In a drilled hole, the circumferential wall portions are pressed against a wall of the drilled hole and the expansible fixing plug is consequently wedged and anchored in the drilled hole. Since the expanded circumferential wall portions abut the wall of the drilled hole virtually over the entire circumference and over the entire length, the result is a large-area, virtually full-face contact with the wall of the drilled hole, which produces a high holding and anchoring force. In porous building materials, such as gas concrete, or in hollow building materials, such as cavity blocks, the large-area contact with the wall of the drilled hole leads to a low load per area unit and hence also to a high holding and anchoring force.
A further advantage of the expansible fixing plug according to the invention is that its expansion ribs abut the pin-shaped expansion element only for part of the circumference and do not completely surround the pin-shaped expansion element. This leads to reduced resistance to driving in, in the case of an expansion screw as the expansion element, to a reduced driving-in torque for the same expansion of the expansible fixing plug.
The expansible fixing plug according to the invention is preferably divided in the expansion region into two circumferential wall portions, from which the expansion ribs project inwards. The circumferential wall portions and the expansion ribs encircle the expansion element that can be inserted between them to an angle of contact of about 180xc2x0. It is nevertheless possible for the expansible fixing plug to be constructed in the expansion region with more than two circumferential wall portions. To guide the pin-shaped expansion element, in one construction of the invention the expansible fixing plug comprises a shank barrel closed all round, which guides the pin-shaped expansion element axially. For pre-assembly, the pin-shaped expansion element can be introduced at little way into the shank barrel and be held there by positive and/or non-positive engagement. The pre-inserted expansion element does not extend into the expansion region, so that the expansible fixing plug is not expanded. The already pre-inserted expansion element simplifies manipulation of the expansible fixing plug.
To enable the expansible fixing plug according to the invention to be manufactured from plastics material as an injection-moulded part, one construction of the invention provides for the circumferential wall portions to be joined to one another so as to articulate by means of a film hinge. The film hinge is a thin plastics material skin, which joins the circumferential wall portions to one another and which acts a hinge by virtue of its thin construction and the flexibility of the plastics material and allows the circumferential wall portions to articulate. The circumferential wall portions can be injection moulded arranged in a line one behind the other or laterally next to one another and after removal from the mould are closed together so that their expansion ribs become interleaved. One circumferential wall portion is preferably directly integrally connected with the shank barrel, and the other circumferential wall portion is indirectly connected to the shank barrel by means of the film hinge and the other circumferential wall portion. After being dosed together, the other circumferential wall portion can be connected to the shank barrel, for example, by ultrasonic welding.
In another construction of the invention, in a starting or original state of the expansible fixing plug following injection moulding, the circumferential wall portions, on the inner sides of which the expansion ribs are mounted, are arranged spaced from one another by a distance such that the expansion ribs are not, or only slightly, interleaved. Between the circumferential wall portions and passing transversely right through the expansible fixing plug there is therefore between the expansion ribs an uninterrupted space, which allows an injection moulding tool to be opened and the expansible fixing plug according to the invention to be removed after injection moulding. The circumferential wall portions can be arranged parallel to one another. Following removal from the mould, the circumferential wall portions can be pressed so far together that the expansion ribs become interleaved and the expansible fixing plug can be inserted in a drilled hole. This construction of the invention enables the expansible fixing plug to be injection moulded in one piece in a single operation. After injection moulding, the circumferential wall portions need merely to be pressed together, which can possibly be effected by insertion of the expansible fixing plug in the drilled hole. The circumferential wall portions do not need to be closed together. Another advantage of this construction of the invention is that the circumferential wall portions do not have to be joined at their ends to one another or to a shank barrel or the like, for example, by ultrasonic welding.
To be able to join the circumferential wall portions together so that they can be pressed together, that is, so that they are movable, one construction of the invention comprises movable connecting elements at one end of the circumferential wall portions, by means of which the circumferential wall portions are connected in one piece with a shank barrel of the expansible fixing plug. The connecting elements can be webs or the like, which have the required mobility by virtue of their resilience.
In one construction of the invention, the circumferential wall portions comprise snap-fit or locking elements, with which the circumferential wall portions can be connected to one another in the pressed-together state. The snap-fit or locking elements are preferably arranged on the leading or insertion end of the expansible fixing plug remote from the shank barrel. In this construction of the invention, after removal of the expansible fixing plug from an injection moulding tool, the circumferential wall portions are pressed together at the leading end of the expansible fixing plug, so that they interlock with one another there. Towards the rear in the direction of the shank barrel, the circumferential wall portions stand obliquely apart. With the circumferential wall portions held together at its leading end by the snap-fit or locking elements, the expansible fixing plug can be introduced into a drilled hole, the circumferential wall portions being pressed together by the drilled hole for their entire length so that the expansion ribs become interleaved. This construction of the invention has the advantage that, after removal of the expansible fixing plug from the mould and before insertion in a drilled hole, only the circumferential wall portions at the leading end of the expansible fixing plug are pressed together until the snap-fit or locking elements engage, and the expansible fixing plug is then ready for use.
In one construction of the invention the circumferential wall portions are connected to one another via a film hinge.